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Moist 6-inch Chocolate Cake (Single layer)

5 from 29 votes
Elien Lewis
This 6-inch chocolate cake is a moist single-layer chocolate cake frosted with a chocolate Swiss meringue buttercream frosting.
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6 inch cake
Prep Time 20 minutes
Cook Time 30 minutes
Total Time 50 minutes
Servings 8 people

Ingredients
 
 

  • 83 g all-purpose flour
  • 25 g cocoa powder natural or dutch processed
  • 1/2 teaspoon baking powder
  • 1/4 teaspoon baking soda
  • 1/4 teaspoon salt
  • 60 g whole milk
  • 1/2 teaspoon Apple cider vinegar or white vinegar or lemon juice
  • 1 large egg
  • 66 g granulated sugar
  • 50 g soft brown sugar
  • 45 g oil vegetable or melted coconut oil
  • 1/2 teaspoon vanilla paste or extract
  • 60 g hot coffee or use hot water

Chocolate Swiss meringue buttercream

  • 113 g semi-sweet chocolate
  • 2 large egg whites 60g/2 oz
  • 66 g granulated sugar
  • Pinch salt
  • 170 g unsalted butter softened to room temperature.
  • 1/2 teaspoon vanilla paste or extract

Instructions
 

Cake

  • Preheat the oven to 350°F (180°C). Grease and line a 6x3-inch round cake pan with parchment paper.
  • Whisk together the flour, cocoa powder, baking powder, baking soda, and salt in a bowl. Set aside. 83 g all-purpose flour, 25 g cocoa powder, 1/2 teaspoon baking powder, 1/4 teaspoon baking soda, 1/4 teaspoon salt
  • Measure the milk, add the vinegar, stir, and leave to sit for 2 minutes. 60 g whole milk, 1/2 teaspoon Apple cider vinegar
  • In a separate bowl, whisk together the egg, sugars, oil, and vanilla. 1 large egg, 66 g granulated sugar, 50 g soft brown sugar, 45 g oil, 1/2 teaspoon vanilla paste or extract
  • Add the dry ingredients to the wet in thirds, alternating with the milk mixture, folding gently with a spatula after each addition.
  • Pour in the hot coffee and fold until just combined. Do not overmix. 60 g hot coffee
  • Pour the batter into the prepared pan and bake for 30 to 35 minutes, until a skewer inserted in the center comes out clean.
  • Run a knife around the edge to loosen. Cool in the pan for 15 minutes, then turn out onto a wire rack and cool completely before frosting.

Chocolate Swiss Meringue Buttercream

  • Melt the chocolate in a microwave-safe bowl in 20 to 30 second bursts, stirring after each, until fully melted. Set aside to cool to room temperature. 113 g semi-sweet chocolate
  • In a clean, grease-free metal bowl (either the bowl of your stand mixer or another metal bowl), combine the egg whites, sugar, and salt. Set over a pot with 1 inch of gently simmering water, making sure the bottom of the bowl does not touch the water. Do not use a glass or ceramic bowl as it can crack or shatter. Whisk constantly until all the sugar has dissolved and the mixture reaches 160°F (71°C) on an instant-read thermometer. 2 large egg whites, 66 g granulated sugar, Pinch salt
  • If you used a separate metal bowl, transfer the mixture to the bowl of your stand mixer now. Fit the whisk attachment and beat on medium-high speed until stiff, glossy peaks form and the bowl is completely cool to the touch, about 8 to 10 minutes.
  • With the mixer running on medium speed, add the softened butter one cube at a time, waiting until each cube is fully incorporated before adding the next. The mixture may look curdled at this stage. Keep beating and it will come together.170 g unsalted butter
  • Beat in the cooled melted chocolate and vanilla until the buttercream is smooth and fluffy. 1/2 teaspoon vanilla paste
  • Switch to the paddle attachment and beat on low speed for 5 to 10 minutes to remove the larger air bubbles.

Assemble

  • Spread the buttercream generously over the top and sides of the cooled cake. Decorate as desired. Store leftover cake at room temperature in an airtight container for up to 3 days, or refrigerate for up to 5 days.

Notes

  • Coffee: Substitute hot water if preferred. The finished cake will not taste like coffee.
  • Buttercream troubleshooting: If the buttercream looks curdled, keep beating and it will come together. If it looks soupy, refrigerate the bowl for 10 minutes then re-whip.
  • Clean equipment: The bowl and whisk must be completely grease-free before whipping the egg whites or they will not whip properly.
  • Storage: Unfrosted cake can be wrapped and frozen for up to 3 months. Buttercream can also be frozen for up to 3 months. Thaw in the fridge overnight, bring to room temperature, and re-whip the buttercream before using.
  • Leftover egg yolks: Use them in these egg yolk cookies.

Nutrition

Serving: 1sliceCalories: 322kcalCarbohydrates: 34gProtein: 3gFat: 21gSaturated Fat: 10gPolyunsaturated Fat: 9gTrans Fat: 1gCholesterol: 31mgSodium: 261mgFiber: 2gSugar: 23g
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